1. Field of the Invention
The present invention relates to a tire changing apparatus for mounting and dismounting tires from their rims. Typically, when a tire is mounted or dismounted from its rim, a tire changing machine is used in which the tire and wheel assembly are placed on a contoured table and over a center post. The tire is then secured to the table by a hold-down cone located around the center post. A tool which is similar to a tire iron having a slot is inserted between the tire and rim. This tool is often referred to as a combination tool. The tire iron is then rotated by hand to lift the tire bead over the rim. The hand rotation is continued until the tire iron slot is in full contact over the center post key. A foot pedal is then engaged and the center post key rotates counter clockwise, moves the tire iron and thus removes the upper tire bead from the rim. Specifically the claimed invention relates to a tire changing machine with a center post key that lockably holds the tire iron in place so that it cannot be dislodged accidentally during its mounting on the center post or during its rotation to remove the tire frm the wheel.
2. Description of the Prior Art
Tire mounting devices are well known in the prior art. For example, the Coats 40-40A mounting machine includes a contoured table top, a center post extending therefrom, a hold-down cone and a center post key. In the operation of the 40-40A machine, the tire iron is mounted onto a center post key or spindle which rotates during the mounting and demounting procedure. However, there is a problem in the prior art in that a springback condition manifests itself when the tire iron is placed over the center post key. The tire iron weighing about 7 pounds tends to flip back towards the operator in what is called a springback condition with resulting risk of injury to the operator. In the cycling mode the springback condition also occurs, particularly if the machine surges during cycling.
Attempts to solve the problem have been made. For example, a hole has been drilled in the center post key for receipt of a nut and bolt or a ball lock pin to secure the tire iron in place. However, such an arrangement is cumbersome. As a result of the number of additional steps required, the operator often will not take the time to insert the bolt and nut.